textproduct: Albany

WHAT HAS CHANGED

Wind Advisory issued for parts of western New England and the Taconics starting late tonight through Tuesday morning to account for wind gusts up to 50mph with initially south to southeast winds through the day tomorrow shift to the west-northwest by Tuesday morning.

A Flood Watch was issued for Litchfield County, CT and Berkshire County, MA to account for poor drainage flooding and river rises on main stem rivers and creeks starting late tonight through Tuesday morning. Latest river forecasts from the Northeast River Forecast Center show river responses on the Hoosic and Housatonic Rivers due to 1 to 2.5 inches of rain.

Marginal Risk (level 1 of 5) in the Day 2 Convective Outlook from the Storm Prediction Center was expanded further north/east into the Capital District, southwest Adirondacks, and the mid- Hudson Valley where there is a 5% chance for damaging winds from severe thunderstorms tomorrow into tomorrow night.

KEY MESSAGES

1) Moderate confidence for strong, gusty winds tomorrow into tomorrow night resulting in downed tree branches and isolated power outages. There is a 50 to 80% chance for wind gusts to reach or exceed 40mph between 2AM Monday and 2AM Tuesday and a 30 to 60% chance between 2AM Tuesday and 2AM Wednesday.

2) Moderate confidence for periods of rain, heavy at times tonight into tomorrow night with even a marginal risk for severe weather mainly for areas near and west of the Hudson River. The heavy rain falling on top of an already saturated ground can result in poor drainage and urbanized flooding in addition to minor river flooding (especially in western New England).

3) There is a low to medium chance for slippery travel for the Tuesday morning commute from the Capital District northward due to wet surfaces potentially refreezing from rapidly cooling temperatures and rain changing to snow for a brief period Monday night into Tuesday.

DISCUSSION

KEY MESSAGE 1...

Latest satellite imagery shows our rapidly intensifying cyclone in the Central Plains with its attendant mid-level warm front lifting through the Northeast. We remain mainly dry through 03 UTC tonight as large scale subsidence under the downstream ridge persists; however, as the sfc warm front start to lift northward tonight, strengthening southeast winds ahead of it will result initially upslope driven showers along the south and eastern slopes of the the eastern Catskills, the southern Greens, and the southern Adirondacks between 03 - 06 UTC. With sfc temperatures still around freezing, these initial showers look to fall as some freezing rain which can lead to slippery travel conditions. However, still held off on any winter weather advisory given the higher terrain locations, overnight timing, and general short duration to any icing. This can handled with a Special Weather Statement, if needed. Southerly winds ahead of the nearly full latitude trough extending down the Gulf States will start to advect moisture from the Gulf into the Northeast overnight with PWATs surging near 1 inch. An area of shortwaves ahead of the incoming sfc warm front will promote lift and focus precipitation into areas of steady rain. This combined with some elevated instability and showalters dropping towards 0 (especially in western New England) may also support some pockets of thunderstorms which will be capable of brief heavy downpours from 06 - 15 UTC.

After 15 - 18 UTC Monday, the sfc warm front should finally lift northward through eastern NY and western New England with temperatures turning quite warm rising into the 50s and low 60s in the warm sector. While a very impressive 50-60kt low level jet will become directed into the Northeast during the morning hours, forecast soundings continue to show a sharp low-level inversion around 925 hPa which should limit mixing. However, this inversion starts to erode by 18 - 21 UTC and with such a notable jet in the 925 - 850 hPa layer, we erred on the side of caution and issued a wind advisory for western New England and the Taconics starting at 18 UTC Monday which typically experience strong, gusty winds in these southeast wind regimes due to downsloping off the Berkshires and southern Greens. We then expanded the wind advisory into the Greater Capital District and the eastern Catskills starting at 21 UTC as the inversion continues to erode. Guidance from the NBM also favors this timing showing increased probabilities for gusts over 30 - 40mph during this window in these areas. Otherwise, only expecting isolated to scattered shower activity late tomorrow morning into the afternoon with showers favored in western New England. Weak elevated instability persist so maintain slight chance thunderstorm wording through tomorrow afternoon with brief heavy downpours possible during any storms.

Immediately behind our incoming cold front Monday night, winds shift sharply to the west and remain quite strong. While the impressive low level jet will shift into New England as the front sweeps through the region, forecast soundings show boundary layer mixing deepening in response to the strong cold air advection that commences. The top of the mixed layer reaches 40 to even 50kts through Tuesday morning in the wind advisory areas so that's why we have our wind advisory going through 15 UTC Tuesday. Probabilistic guidance even shows 30 to 60% chance for gusts to exceed 40mph 2AM Tues to 2AM Wed with the best chance for this immediately behind the cold front Monday night through midday Tuesday. Winds remain gusty through Tuesday afternoon but gradually weaken as the cyclone exits.

KEY MESSAGE 2...

Our parent cyclone will deepen further tomorrow afternoon as it heads into the Great Lakes and becomes negatively tilted. Rapid height falls ahead of it will spill into the Northeast by tomorrow evening with the screaming 50-70kt southerly jet maintaining anomalously high moisture transport (4 to 6 standard deviation above normal per the NAEFS) into the Northeast. While shower coverage increases tomorrow evening, the main line of moderate to heavy rain focused immediately ahead of the approaching cold front looks delayed until 03 - 06 UTC Tuesday due to the highly amplified flow. Unidirectional flow parallel to the boundary through a deep layer and low-level convergence within the mild and highly moist environment will support efficient warm rain processes. In fact, the 3-hourly ensemble mean QPF amounts from the HREF range between 0.25 and 0.75" for areas near and west of the Hudson River through 06 UTC Tuesday. While instability ahead of the front will weaken as the front shifts into eastern NY Tuesday night, even the limited 100 to 200 J/kg MUCAPE may be enough to support convective elements and heavy downpours. The unidirectional flow also means the the heavy rain may linger over a given area for a few hours, supporting the potential for urban and poor drainage flooding.

As the front heads east of the Hudson River near/shortly after 06 UTC Tuesday, the heavy rainfall rates looks to diminish as the main parent cyclone and stronger forcing escapes into southern Canada. Still expecting moderate rainfall rates but the probability for heavy rainfall rates decreases as the front reaches western New England. Total rainfall amounts between late Sunday and Monday night looks to range between 1 and 2.5 inches with the highest amounts in western New England and the eastern Catskills. Issued a flood watch for western MA and NW CT from late tonight through 12 UTC Tuesday given the 40 - 50% ground saturation seen in the FLASH guidance overlapped with the highest QPF amounts, potential for heavy downpours during any storms and rivers already running high. Main concern will be poor drainage/urbanized flooded and rises on main stem river and creeks. While the latest forecasts from the Northeast River Forecast Center do not show rivers exceeding flood stage, latest MMEFS guidance shows 10 to 30% chance for minor flood stage on the Hoosic, Housatonic and Walloomsac Rivers so felt a Flood Watch helped message the flood potential.

Given the very high shear yet low CAPE environment, we will also monitor the potential for severe weather along the main cold front Tuesday night. Latest Day 2 Outlook from SPC expanded the marginal into our western zones up to the Hudson River; however, given the overnight timing and limited opportunity to destabilize the air mass ahead of the front, any QLCS or convective line that develops will likely weaken as it tracks into eastern NY. It is hard to ignore the impressive 50kt+ 0-6km deep layer shear but the lack of instability should dampen the severe potential. Should any stronger storms reach our western zones, damaging winds would be the primary hazard.

KEY MESSAGE 3...

As if the flood and gusty wind potential were not enough, we also need to monitor the potential for rain to change over to sleet/snow as the front sweeps through the region Monday night. While the main parent cyclone escapes into southern Canada, strong upper level divergence looks to aid in the development of a secondary low along the cold front Monday night. This should maintain sufficient precipitation behind the boundary as temperatures rapidly drop between 03 and 09 UTC Tuesday. Latest probabilistic guidance shows the highest chance for at least a half inch of snow in the southern Adirondacks, Mohawk Valley and northern and eastern Catskills with values ranging 40 to 80% while values drop to 20 to 40% in the Taconics, higher terrain areas of western MA, and southern VT. Probabilities lower to only a 10 to 25% chance in valley areas from the Capital District into the Upper Hudson Valley but this can still lead to slippery travel for the Tuesday morning commute as the wet ground can quickly refreeze and stay icy underneath even minor snow accumulations. Morning low temperatures by Tuesday morning look to drop into the mid to upper 20s regionwide.

Should precipitation end earlier, there may not be enough QPF when temperatures cool enough to support a transition to snow/sleet. This would lower snowfall amounts on the backside, especially in valley areas, but it would not reduce the refreeze and slippery travel potential as rainfall ends by 06 - 09 UTC. There may not be enough time for the gusty westerly winds to dry out surfaces before temperatures drop into the 20s by early Tuesday A.M.

AVIATION /20Z SUNDAY THROUGH FRIDAY/

VFR conditions are expected prior to 00Z/MON for KGFL/KALB/KPOU/KPSF with bases mainly in the 3.5-7 kft AGL range, as clouds thicken and lower. A high MVFR cig may get close to KPOU between 22Z/Sun and 00Z/Mon, as deeper low-level approaches ahead of a warm front and a strong low-level jet. Clouds thicken and lower into the MVFR range initially with showers spreading northward gradually between 04Z- 09Z/Mon. Flight conditions will lower into the lower MVFR/IFR range with the showers/rain. A few rumbles of thunder may impact KPOU after 09Z/Mon, but we did not include in the TAF yet with low probabilities. In the deeper moisture, ahead of the warm front widespread IFR conditions are expected to develop 09Z-13Z/SUN in terms of cigs/vsbys at the TAF sites with the rain tapering to drizzle or spotty showers for the late morning into the early pm.

LLWS will become an issue at KGFL/KPOU/KPSF between 00Z-03Z/Mon at the 2 kft AGL winds increase to 40-50 KT with the sfc winds generally less than 10 KT. LLWS was added later for KALB toward 09Z/MON with the sfc winds decreasing and the 2 kft winds 40 KT. LLWS wind shear was kept in all the TAF sites until the end of the TAF cycle with the low-level jet/2 kft AGL winds at 40-55 KT.

The winds will increase from the east to southeast 5-10 KT prior to 00Z/Mon with some gusts around 20 KT at KALB/KPSF. The east to southeast winds will persist around 5-12 KT with some gusts around 25 KT at KALB overnight, but rainfall may decrease the gusts for a brief time. South to southeast winds at 5-15 KT will continue from the late morning into the afternoon.

Outlook...

Monday Night: High Operational Impact. Windy With Gusts To 38 kts. Definite SHRA...SHSN...RA. Tuesday: Moderate Operational Impact. Windy With Gusts To 35 kts. NO SIG WX. Tuesday Night: Low Operational Impact. Breezy. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Low Operational Impact. Slight Chance of RA. Friday: Low Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Flood Watch from late tonight through Tuesday morning for CTZ001-013. Wind Advisory from 2 PM Monday to 11 AM EDT Tuesday for CTZ001- 013. NY...Wind Advisory from 2 PM Monday to 11 AM EDT Tuesday for NYZ054- 061-066. Wind Advisory from 5 PM Monday to 11 AM EDT Tuesday for NYZ048>053-058-063-084. MA...Flood Watch from late tonight through Tuesday morning for MAZ001-025. Wind Advisory from 2 PM Monday to 11 AM EDT Tuesday for MAZ001- 025. VT...Wind Advisory from 2 PM Monday to 11 AM EDT Tuesday for VTZ013- 014.